The present invention relates to palletizers and to wrapping articles stacked on palletizers and more particularly, to a novel method and apparatus for wrapping articles on pallets in such a manner as to prevent the items being wrapped from either being crushed or from shifting their position and using less expensive and less complicated equipment than that used in conventional systems.
Conventional materials handling techniques incorporate the use of pallets, which are typically moved about, with or without loads, by forklift trucks and the like. These techniques have been proven to be effective from the point of view of both cost and efficiency. In order to stabilize loads placed on pallets and especially loads having shapes which deviate from shapes which easily stack and retain their stability, such as cardboard cartons and the like, it is necessary to use a wrapping film, which is wrapped about the perimeter of the load.
For example, it is conventional to successively load layers of items upon a pallet and to wrap the layers of items, assembled on the pallet, with a stretch film to thereby stabilize the completed load for subsequent transportation and handling.
As each layer is placed upon a pallet, the wrapping film, which is typically a stretch film, is stretched as it is wrapped around each completed layer deposited on the pallet.
Typically, since the wrapping film is stretched during application, some or all of the forces required to stretch the film are transferred to the products being wrapped on the pallet. This force disturbs the products and especially their positioning, resulting in a poorly wrapped pallet load. The forces exerted upon the products loaded upon the pallet may even crush the products in the event that they are capable of being crushed and/or may displace the articles or products from the desired position that they were originally placed upon the pallet, which shifting of position affects both the stability and integrity of the wrapped load, and often results in products being crushed and/or falling off of the loaded pallet.
One technique, which has partially solved the above problems, is the utilization of a powered stretch wrap applicator head, which includes a means for driving the film at a speed or speeds that are independent from the wrapping cycle, thereby reducing the force imparted to the products being wrapped. This technique necessitates the use of a motor-driven, film pre-stretching roller assembly and a cooperating sensing device mounted to move along a circular track in order to properly wrap the film about the load, which is expensive and also necessitates significantly more rugged structural members to support this assembly.
In addition, when wrapping loads on a pallet comprised of unstable and/or irregularly shaped products, the wrapping problem is compounded in two ways: 1) each layer of products that is placed on a pallet in a predetermined, desired array, can become disoriented and displaced by a previously applied layer of products due to the effect of the irregular shapes of the products; and 2) the irregular shapes of the products cause the stretched film material to collapse into the spaces between layers of products, which results in unevenly wrapped, loaded pallets and requires additional wraps of stretch film to stabilize the load thereby increasing both the cost and the cycle time of loading a pallet, leading to a significant reduction in the efficiency of the pallet loading operation. This problem is quite prevalent in the loading and wrapping of newspaper bundles and especially, those having a number of different shaped inserts, causing the bundles, when wrapped, to assume a shape referred to in the newspaper bulk handling industry as xe2x80x9cwatermelonsxe2x80x9d or xe2x80x9cfootballsxe2x80x9d.
Although the first-mentioned problem may be resolved, at least partially, by placing a sheet of material (typically referred to as a xe2x80x9ctier-sheetxe2x80x9d) between each layer of products, this operation increases the overall cycle time, as well as the cost of the loading and wrapping operation.
Prior to the advent of the present invention, no suitable solution has been developed for resolving the second-mentioned problem.
The above, as well as other problems in conventional palletizing and load wrapping techniques are solved by use of a method and apparatus which is characterized by comprising guides which are arranged along all of the sides of a layer of products, which layers of products are moved downwardly through the aforesaid guides, which guides both define and limit the perimeter of the layer. The guides are generally perpendicular to the top loading surface of a pallet, which layers pass downwardly through the guides as the pallet is successively lowered to receive each layer of products.
As the pallet passes beneath the lower edges of the guides, the layers formed on the pallet are initially contained by the side guides. The guides, together with the stretch wrap and the manner of application, are especially advantageous in retaining a layer of unstable articles, such as xe2x80x9cwatermelonxe2x80x9d and/or xe2x80x9cfootballxe2x80x9d shaped articles and the stretch wrap film, being looped about and engaging both the guides and pallet, surrounds and secures the unstable layer as it passes below the lower edges of the guides, thereby preventing the unstable layer from falling off of the pallet.
A wrapping film, preferably, a stretch wrap film, is dispensed from a supply roll and is wrapped about the perimeter of the pallet and the lower portion of the first layer of products, resting on the pallet, the outer sides of which are exposed as the layer of products on the pallet starts to move below the guides, together with the lowering of the pallet relative to the guides.
The initial wrapping of the stretch film about all four sides of the pallet and partially exposed outer sides of the first layer of products resting upon the surface of the pallet, covers these exposed portions, as well as at least a lower portion of the guides, thereby forming a rectangular-shaped tube or loop of stretch wrap material firmly and tightly wrapped about the perimeter of the pallet and the outer surfaces of the guides so that forces that might otherwise be imparted to the products by the wrapping and stretching of the film about the product layer, are predominately imposed upon the pallet and the guides, as opposed to the exposed portion of the product being wrapped, which prevents the stretch film from displacing and/or crushing the products in the layer being wrapped.
As the first layer of product is wrapped by the stretch film, each successive new layer is assembled above the pallet and placed on previously formed layers. The pallet and successive layers placed thereon, continue to move downwardly relative to the side guides as the pallet is typically lowered so that there becomes a time at which the assembled layers are fully exposed below the side guides.
Each rectangular-shaped tubular portion or loop of stretch wrap film wrapped about the load and positioned between the pallet and the outer surfaces of the guides, serves to hold each product layer in place, preventing each wrapped layer from falling off of the pallet being loaded.
During subsequent wrapping cycles, as each completed loop of stretch film wraps about an upper portion of a previously wrapped layer, the top portion of the film continues to be wrapped about the outer surfaces of the guides, with the result that the film wrapping forces on each newly wrapped layer is minimized and the problem of the film collapsing into the spaces between the regularly shaped products is eliminated or significantly reduced.
The aforementioned upper portion of the stretch film, which is wrapped about the guides, applies a force to the guides and is hence under tension, which may cause the stretch wrap film to retain its grip and/or stick to the guides. These wrapping forces are most prevalent at the corners of the guides. In order to eliminate, or at least, significantly reduce these forces, to enable the loop of shrink wrap film to freely move away from the guides, the guides, in one preferred embodiment of the present invention, include means for periodically creating a film of air between the engaging surfaces of the guides and the loop of stretched film wrapped therearound, enabling the loop of stretch wrap film to move downwardly and away from the guides as the layer of products having the lower portion of the stretch wrap film looped therearound is lowered relative to the guides, enabling the present loop of stretch wrap film to move downwardly in readiness for wrapping the next loop of stretch wrap film, partially about an array of products and partially about the guides. This operation is continued until the final and topmost layer of product is deposited upon the pallet whereupon the terminating loop has its free end secured to the outermost layer of stretch wrap film engaged by the free end.
The aforementioned pallet loading system also includes apparatus for storing empty pallets and delivering stored, empty pallets, one at a time, to a pallet loading station in synchronism with apparatus for receiving, arranging and depositing arrays of products upon a pallet, as well as apparatus for ejecting pallets which have been loaded with product and fully wrapped, to an exit location in readiness for delivery to utilization devices, such as, conveyors, forklift trucks and the like, for conveying loaded pallets to loading bays for loading upon trucks or the like.
The shrink wrap film looped about the guides may be released from the guides by alternative embodiments other than the xe2x80x9cair filmxe2x80x9d technique, described above, such as: angling the guides and forming guides of a surface material having a low coefficient of sliding friction.
As was mentioned above, the method and apparatus of the present invention produces a wrapped load on a pallet which is stable and will not shift when moved and is not subjected to crushing by the stretch wrap film, all of which is accomplished through the use of apparatus which is simpler in design and use, and is less expensive than conventional power driven apparatus.
It is therefore one object of the present invention to provide novel method and apparatus for wrapping palletized loads comprised of layers of articles, by employment of guides which retain a layer of unstable articles, such as xe2x80x9cwatermelonxe2x80x9d and/or xe2x80x9cfootballxe2x80x9d shaped articles, to prevent such articles from falling and looping stretch wrap film about portions of the guides and the pallet to prevent articles from falling off the pallet as the articles move downwardly below the lowers edges of the guides.
Another object of the present invention is to provide a novel method and apparatus for wrapping arrays of product successively deposited upon a pallet by wrapping the perimeter of an array of products together with guides through which the arrays descend to prevent the wrapping material from damaging or displacing the arrays and further to prevent the wrapping film from collapsing into the regions between successive layers.
Still another object of the present invention is to provide a novel method and apparatus for wrapping layers of products deposited upon a pallet or the like in which the wrapping material, typically, a shrink wrap film, is wrapped about both the perimeter of the arrays and guides through which the arrays descend and further for providing techniques for releasing the film wrapped about the guides from the guides to assure smooth continuous wrapping of the layers of products.
Still another object of the present invention is to provide a novel method and apparatus for wrapping film about arrays of products deposited upon a pallet or the like, which prevents collapsing of the wrapped loops of the wrapping film and which further eliminates the need for applying multiple loops of wrapping film in regions the film would otherwise collapse into the recesses between adjacent arrays, but for the novel method and apparatus of the present invention and further in which the wrapping method and apparatus are integrated into an overall system which automates the delivery of empty pallets, delivery of products and arranging products into arrays and depositing arrays upon an empty pallet or upon an array of products previously delivered to the pallet, all of which are performed in an automated and synchronized fashion.